With minuteness of a semiconductor pattern, a slight shape difference affects an operation characteristic of a device and needs for shape management increase. For this reason, in a scanning electron microscope (SEM) used for inspecting and measuring a semiconductor, high sensitivity and high precision are required increasingly. In the SEM, when an electron beam irradiates a sample, secondary electrons emitted from the sample are detected and a shape of a surface is observed. At this time, the detected secondary electrons have low energy and are affected by electrification of the sample. Due to recent minuteness of a pattern or a use of a low permittivity material such as low-k, effects from the electrification become obvious and it may become difficult to capture a signal of a place where management is necessary.
In this case, because the energy of the secondary electrons emitted at the time of irradiation of the electron beam does not change, changing of the state of the electrification of the sample surface becomes a solution. A method of changing an irradiation current amount and improving a detection rate of a foreign material is disclosed in PTL 1. In addition, a method of changing a scan interval of an electron beam according to electrification time constant of an observed sample and suppressing electrification of a surface is disclosed in PTL 2. A method of changing a scan speed of a partial area in a field of view (FOV) and controlling an electrification state distributed on a surface is disclosed in PTL 3.